This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2002-64024, filed Mar. 8, 2002, the entire contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a disk apparatus for reading a magnetic disk or an optical disk, and to a condensation preventing member used in the disk apparatus.
2. Description of the Related Art
Known disk apparatuses includes for example, a magnetic disk apparatus such as a hard disk drive and an optical disk apparatus such as a CD-R drive.
For example, a magnetic disk apparatus comprises constituting parts such as a magnetic disk, a magnetic disk driving mechanism, a recording-reading magnetic head, and a carriage assembly, which are arranged compact within a base body, and a lid body covering the base body. In the magnetic disk apparatus of the particular construction, the magnetic head is allowed to float on the magnetic disk that is rotated at high speed so as to carry out the recording and reading of information. If the base body and the lid body are hermetically sealed so as to permit the constituting parts noted above to be completely shielded from the outer atmosphere, an undesirable change in the gaseous pressure, which gives rise to an inconvenience in the floating of the magnetic head, is generated in the vicinity of the magnetic disk rotated at high speed. Therefore, air passageways sized and constructed not to permit, for example, dust to enter the base body are formed in advance in the base body so as to introduce the outer air into the base body in an amount large enough to achieve floating of the magnetic head. However, since the outer air is introduced into the base body, the magnetic disk apparatus is likely to be affected by the environment so as to bring about a change in the humidity within the magnetic disk apparatus. If the humidity within the magnetic disk apparatus is increased, the magnetic head tends to be drawn to the surface of the magnetic disk, with the result that it is impossible for the magnetic head to float stably on the magnetic disk. On the other hand, if the humidity within the magnetic disk apparatus is low, static electricity tends to be generated within the magnetic disk apparatus. It should be noted that, if an excessively large current flows electrostatically through the MR or GMR element generally used in a magnetic disk, an electrostatic rupture tends to take place. In each of these cases, a problem is generated that it is difficult to achieve an accurate magnetic recording-reading operation.
Under the circumstances, the magnetic disk apparatus is constructed in general such that, in order to control the humidity within the base body so as to prevent condensation and electrostatic rupture, a filter or a patch housing a moisture absorbing agent is housed in the base body.
Proposed in, for example, Jpn. Pat. Appln. KOKAI Publication No. 7-14378 is a magnetic disk apparatus equipped with a so-called xe2x80x9chighly hygroscopic resinxe2x80x9d, i.e., a moisture absorbing agent whose moisture absorbing characteristics are increased with increase in the humidity and with a so-called xe2x80x9cA type silica gelxe2x80x9d, i.e., a moisture absorbing agent whose moisture absorbing characteristics decrease as the humidity increases. In this prior art, two kinds of moisture absorbing agents noted above are used such that the highly hygroscopic resin performs its function at high humidity so as to prevent the high humidity and the A type silica gel releases moisture at low humidity so as to prevent the low humidity. In this fashion, a change in the humidity within the apparatus is suppressed over a long period.
In the prior art quoted above, however, the hygroscopic characteristics of the moisture absorbing agent used are particularly high. Where a temperature-humidity cycle test was conducted, the moisture absorbed by the moisture absorbing agent was not released sufficiently, with the result the moisture absorbing capability of the moisture absorbing agent was gradually reduced with time. In other words, the prior art quoted above gives rise to the problem that, even if the moisture absorbing agent is arranged, the humidity within the magnetic disk apparatus is increased if the temperature-humidity cycle is repeated.
An embodiment of the present invention, which has been achieved in an attempt to overcome the above-noted problem inherent in the prior art, may provide a disk apparatus having a long life and high reliability, which uses a moisture absorbing agent capable of effectively suppressing the change in humidity within the disk apparatus so as to prevent malfunction caused by the condensation.
According to a first aspect of the present invention, there is provided a disk apparatus, comprising:
a base body;
a disk medium, a driving mechanism for supporting and rotating the disk medium, a head equipped with an element for reading the information recorded in the disk medium, a carriage assembly supporting the head in a manner to be movable relative to the disk medium, and a condensation preventing member, which are placed on the base body; and
a lid body covering the base body;
wherein the condensation preventing member contains a moisture absorbing agent exhibiting a different moisture absorption amount depending on the humidity, the difference in the moisture absorption amount in its hygroscopic isothermal line between the moisture absorbing agent at a relative humidity of 80% and the moisture absorbing agent at a relative humidity of 95% being not less than 30% in the moisture absorbing stage and not less than 20% in the moisture releasing stage based on the dry weight of the moisture absorbing agent.
According to a second aspect of the present invention, there is provided a disk apparatus, comprising:
a base body;
a disk medium, a driving mechanism for supporting and rotating the disk medium, a head equipped with an element for reading information recorded on the disk medium, a carriage assembly supporting the head in a manner to be movable relative to the disk medium, and a condensation preventing member, which are placed on the base body; and
a lid body covering the base body;
wherein the condensation preventing member contains a moisture absorbing agent including at least first and second components each exhibiting a different moisture absorption amount depending on the humidity;
the difference in the moisture absorption amount in its hygroscopic isothermal line between the first component of the moisture absorbing agent at a relative humidity of 80% and the first component of the moisture absorbing agent at a relative humidity of 95% is not less than 30% in the moisture absorbing stage and not less than 20% in the moisture releasing stage based on the dry weight of the first component of the moisture absorbing agent; and
the difference in the moisture absorption amount in its hygroscopic isothermal line between the second component of the moisture absorbing agent at a relative humidity of 40% and the second component of the moisture absorbing agent at a relative humidity of 65% is not less than 20% in the moisture absorbing stage based on the dry weight of the second component of the moisture absorbing agent, and the difference in the moisture absorption amount between the second component of the moisture absorbing agent at a relative humidity of 20% and the second component of the moisture absorbing agent at a relative humidity of 50% is not less than 20% in the moisture releasing stage based on the dry weight of the second component of the moisture absorbing agent.
Additional embodiments and advantages of the present invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the present invention. The embodiments and advantages of the present invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.